The present invention relates to a method of producing a frame made of connected semiconductor die mounting substrates which can be preferably used for producing BGA (ball grid array) type semiconductor devices with high productivity and high reliability, and more particularly used for BGA type semiconductor devices each of which is substantially made of semiconductor die mounting substrate which mounts a lead pattern on one surface thereof while making the other surface thereof adhered to a die mounting portion of the metal substrate.
Conventionally, the semiconductor devices such as IC (integrated circuit) and LSI (large scaled integrated circuit) are mounted in such a manner that a plurality of outer leads which are formed in a desired shape such as a J-shape or a gull-wing shape along an outer periphery of the semiconductor device are protruded outwardly and such outer leads are connected with corresponding mounting pads (or lands) of a wiring pattern formed on a mounting board of a printed wiring board (PWB) by soldering. This method, however, necessitates a relatively wide mounting region so that the method cannot meet a demand for compacting of the semiconductor devices.
For overcoming this drawback, recently, the semiconductor devices called BGA which use a plurality of solder balls as the outer connecting terminals of semiconductor devices thus realizing miniaturing of semiconductor dies, down-sizing of the semiconductor devices and lowering of the production cost of the semiconductor devices have been proposed. Such devices are, for example, disclosed in U.S. Pat. No. 5,045,921 (Lin et al.), U.S. Pat. No. 5,216,278 (Lin et al), U.S. Pat. No. 5,397,921 (Karnezos), U.S. Pat. No. 5,420,460 (Massingill), Japanese laid-open patent publication HEI 3-99456 and Japanese laid-open patent publication HEI 4-277636.
In mounting such semiconductor devices on the mounting board, soluble solder balls of each semiconductor device are first aligned with corresponding mounting pads or lands of the mounting board and subsequently are mounted on the mounting pads and the soluble solder balls are reflown by heating thus enabling a simultaneous mounting of all solder balls to the mounting pads of the mounting board facilitating the mounting of semiconductor devices on the mounting board.
The above-mentioned BGA type semiconductor devices and the die mounting substrates thereof have been produced, for example, by a following method.
Namely, a metal substrate sheet which defines a plurality of longitudinally and laterally arranged unit regions in an abutting relationship is produced from a metal sheet having a favorable heat conductivity, wherein each unit region includes a die mounting portion. Subsequently, a circuit substrate sheet which defines a plurality of longitudinally and laterally arranged unit regions in an abutting relationship is produced, wherein each unit region is provided with an opening at the center thereof and a lead pattern made of a plurality of conductive leads distributed radially around the opening and a solder resist layer which is provided with a plurality of spaces through which the conductive leads are exposed to an atmosphere in an area arrayed manner.
On the surface of the circuit substrate sheet which opposes to the surface thereof on which the lead pattern is provided, the metal substrate sheet is laminated and heat sealed by means of a heat-resistant adhesive layer to produce a semiconductor die mounting substrate sheet 217 shown in FIG. 12. A plurality of longitudinally and laterally arranged unit regions 215 are integarally mounted on the semiconductor mounting substrate sheet 217 and each unit region 215 is provided with an opening 216 at the central portion thereof for mounting a semiconductor die. Subseqeuntly, this semiconductor mounting substrate sheet 217 is cut and separated along lateral and longitudinal separation lines 218 so as to produce a plurality of individual semiconductor die mounting substrates 219 as shown in FIG. 13.
These semiconductor die mounting substrates 219 are mouted on a transfer carrier (not shown in the drawings) or are individually fed to a semiconductor die assembly line and positioned in place and a semiconductor die 221 is mounted on each semiconductor die mounting susbtate 219 by means of an electrically conductive adhesive agent as shown in FIG. 14. Subsequently, a plurality of bonding wires have one ends thereof connected with corresponding ends of a plurality of wire bonding pads 222 and other ends connected with a plurality of electrode terminals mounted on the semiconductor die 221 so as to provide an electrically conductive circuit. Then, as shown in FIG. 14, a potting molding is carried out so as to hermetically seal the semiconductor die 221, the bonding wires, the wire bonding pads 222 and the inner ends of the solder resist layer 223 with a potting resin 224. Finally, a plurality of solder balls which are protruded outwardly from the solder resist layer 223 are connected to a plurality of outer connecting terminals which are exposed on the solder resist layer 223 in a grid array manner so as to produce a semiconductor device 220.
In the above conventional method of producing a semiconductor device, however, the metal substrate sheet and the circuit substrate sheet which are respectively provided with a plurality of separate or individual unit regions are first heat sealed together to form the semiconductor die mounting substrate sheet 217 and subsequently the sheet 217 is cut and separated to produce a plurality of individual semiconductor die mounting substrates 219. Accordingly, at the time of mounting the semiconductor dies 221, the transferring and the positioning of the individual semiconductor die mounting substrates 219 become cumbersome, the quality of the semiconductor devices 211 and the operability of the semiconductor die mounting operation are worsened and the productivity of the semiconductor devices are drastically decreased.
Still furthermore, the accurate positioning of the respective semiconductor die mounting substrates 219 on the the transfer carrier requires expensive die mounting facilities thus increasing the production cost of semi conductor devices.
Accordingly, it is an object of the present invention to provide a method of producing a frame made of connected semiconductor die mounting substrates for BGA type semiconductor devices which can overcome the above-mentioned drawbacks of the conventional method, wherein the method is preferably used in the manufacturing of semiconductor mounting substrates and can improve the trasferring and positioning efficiency at the time of mounting semiconductor dies on the semiconductor die mounting substrates thus facilitating the mounting of semiconductor dies and eventually enhancing the productivity of the semi conductor devices.
It is another object of the present invention to provide a method of producing a frame made of connected semiconductor die mounting substrates which can utilize existing semicondutor mounting facilities with conventional lead frames for producing the frame made of connected semiconductor die mounting substrates thus obviating the purchasing of new facilities or new transfer carrier jigs and eventually can produce the frames made of connected semiconductor die mounting substrates economically.
It is still another object of the present invention to provide a method of producing a frame made of connected semiconductor die mounting substrates which can obviate the cumbersome transferring and positioning operations which are necessary in the conventional method using the individual semiconductor die mouting susbtrates thus enhancing the operability of the mounting of the semiconductor dies.